Questioning the success rate of CBI in solving cases, West Bengal Chief Minister Mamata Banerjee today described investigation by the agency into Saradha Chit Fund scam as a ploy to save the real culprits and use it to defame the state government.

"You can check the records, the success rate of CBI is very poor. CBI has been used by the party that is at the Centre to corner its political opponents by using malicious and pressure tactics," Banerjee said in an interview to a Bengali news channel.

Banerjee's statement comes in the backdrop of CBI and the Enforcement Directorate closing in on the Saradha money trail and raids and interrogations of various influential persons making headlines everyday.

"I think this investigation is moving in such a direction where this is being used to shield the real culprits. But if someone is thinking that by arresting some people they can a carry out malicious campaign against us then we will not tolerate that," Banerjee said.

She said that these Chit fund companies which under the radar of central security and intelligence agencies had mushroomed in the state.

"These Chit Funds had come up in Bengal during the Left regime. When this chit fund scam came into fore, we arrested the Saradha group chairman (Sudipto Sen) from Kashmir, when allegations were levelled against our Party MP Kunal Ghosh, we didn't spare him either, he was arrested too. We gave back 500 crores to those defrauded investors from our state treasury. We formed the SIT to investigate the scam," said Banerjee.

"I personally want that all the real culprits should be arrested and punished, so we have extended all support to CBI and other central agencies. Rather I am relieved that CBI has taken over the investigation now they will return the money," she said.

Banerjee yesterday had said in a rally that her party does not need chit fund money to run its affairs and warned those who were engaged in "political maligning" of shielding the "real culprits".